Hello and welcome to HCM, The symptoms of irregular bowel movements, alternating diarrhea and constipation, blood mixed stools and feeling of incomplete bowel clearing can be seen two common conditions - inflammatory bowel disease and malignancy or growth in the bowel. A normal colonoscopy has ruled out presence of growth in the large bowel. The other possibility is that of inflammatory bowel disease (IBD). IBD may not produce any specific lesion. Thus, biopsy from multiple sites in the large bowel is required to look for any disease process at microscopic level. Management can be started only when biopsy is taken. Thanks and take care Dr Shailja Puri